Patent GB-469039-A (GB)
Title: Improvements in and relating to copying milling-machines
IPC: B23Q35/18
Filed: 1936-01-18
Abstract: 469,039. Fluid-pressure servomotor-control systems. FITZPATRICK, H. J. (Clearing Machine Corporation) Jan. 18, 1936, No. 1718. [Class 135] [Also in Group XXII] In a copying milling-machine wherein the work and pattern are moved universally in a plane beneath the cutter and tracer, the tracer controls mechanism for moving the work and pattern to and from the cutter and tracer transversely to said plane and additional means are provided acting directly on the tracer to limit the feed of the work to the cutter. Hand-controlled means are also provided acting directly on the tracer for stopping the upward feed at any time. The vertical upward feed of the work table is effected hydraulically under control of a tracer valve and the invention may be adapted as an attachment to an ordinary verticalcolumn knee-type machine. The machine comprises a vertical column 16 having vertical ways for a knee 17 which carries slides 20, 21 moving horizontally at right-angles to each other. The cutter 19 is carried by a fixed bearing 18 on the column and the tracer head 44 by a bracket 84 attached to the column. A split clamp 101, Fig. 2a, secures the head to a slide 98 adjustable on a transverse bearing member 91 by means of a hand wheel and screw 99, the member 91 being splined at 92 within a bracket 90 and movable by a screw and hand wheel 97. The bracket 90 is vertically adjustable in a boss 86 of the bracket 84 by means of a hand wheel 87 and screwed stem 88 on the bracket 90. The tracer head comprises a cylinder 44, Fig. 3, containing a liner 46 provided with inlet and exhaust ports 47, 53 respectively. A piston 56 normally severs communication between these ports, as shown, but may be raised by the tracer to allow fluid to pass from the inlet passage 50 to the exhaust passage 55 by means of an annular recess 57. A pump 33, Fig. 1, supplies fluid from a sump 34 by pipes 36, 51 to the passage 50 and by pipes 36, 37 to two cylinders 29 whose pistons are attached at 32 to the knee 17. The tracer 58 is attached to a stem 65 carrying a flange 59 resting on the annular lip of the bottom cover 61 of the cylinder 44, a lock nut 62 providing for adjustment of the cover in the cylinder. The piston 56 is pressed against the flange 59 by a light spring 71 whose compression is adjustable by means of a plug 77 screwing in the upper cover 73 and locked by a nut 78. A pin 66 on the piston loosely engages the flange 59 to prevent relative rotation thereof, and a drip tray 69 collects fluid which escapes past the piston and conveys it to the sump by means of a pipe 70. In operation, with the piston in the position shown in Fig. 3, the pump supply is delivered to the cylinders 29 to raise the work 80 and pattern 42 on the knee 17 towards the cutter and tracer. When the pattern engages the tracer the piston is moved upwardly and fluid escapes from the port 47 to the port 53, thereby reducing the pressure of the supply to the cylinders 29 and arresting or reducing the upward feed of the work. The slides 20, 21 are given reciprocating movements in the usual manner and the displacements of the piston 56 by the tracer cause the cutter to reproduce the surface curvature of the pattern. The operator may lower the work away from the cutter at any time by rotating a lever 124 pivoted at 125 to the cover 61 and causing a cam surface thereon to rock the tracer spindle 65 and raise the piston 56. A feed limiting stop is also provided comprising a rod 104, Fig. 1, on the knee 17 which may engage a plunger 106 mounted on the bracket 84. Rack teeth on the plunger mesh with a pinion connected by a universally jointed telescopic shaft 113 to a cam 117, Fig. 2a, rotatably mounted above the tracer head 44 and engageable with adjustable collars 119 on a rod 74 secured to the lower end of the piston 56, Fig. 3. A spring normally maintains the plunger 106 depressed, but if the knee 17 ascends too high, the rod 104 raises the plunger and rotates the cam 117 so as to lift the piston 56 and stop further elevation of the knee. The plunger 106 may also be raised at will by the operator through a rod 122 slidable in the bracket 84 and carrying a cam surface engaging a roller on the plunger. The sump 34 is provided with a vent 83, Fig. 1, and a pressure regulating valve 81 and control valve 82 are provided in the pump outlet 36. The pattern 42 may be made of inexpensive soft material.